The present invention relates generally to a torque convertor, and more particularly to a torque convertor comprising a power disconnecting clutch for connecting a torque convertor body (a toroidal member) and an output-side member.
In general, a torque convertor transmits power by means of hydraulic fluid. Wherein such a torque convertor is provided to a manual speed change gear (For example, Japanese Utility Model Laid-Open No. 38355/1989) in order to increase torque at start, a power disconnecting clutch is installed between a turbine in a torque convertor body and an output shaft. A combination of the manual speed change gear and the torque convertor realizes a semi-automatic power transmission device.
In the above described conventional torque converter, hydraulic operating fluid from the torque convertor body enters a space where the power disconnecting clutch is disposed. In the torque converter having such a structure, a large amount of hydraulic operating fluid is supplied to a clutch part. This hydraulic operating fluid functions as lubricating oil. However, the large amount of hydraulic fluid in the clutch part causes drag torque at the time of disconnecting power. When the drag torque is generated, the rotation of the torque convertor is transmitted to an output-side member through each plate, so that it may, in some cases, be difficult to shift gear by the manual speed change gear. Moreover, it is very difficult to control the flow amount of the hydraulic operating fluid entering the clutch part from the torque convertor body. Therefore, it is difficult to achieve both the reduction in the drag torque and the improvement in lubricity.
The power disconnecting clutch is mainly composed of a drive-side member fixed to the turbine, a driven-side member connectable to the output-side member, and a clutch part for connecting and disconnecting both the members to and from each other. The clutch part comprises a plurality of annular plates respectively attached to the drive-side member and the driven-side member so as to be movable in the axial direction and alternately disposed, and a piston for pressing the plurality of plates against each other.
Generally in a dry clutch device, a clutch disk is provided with a cushioning member such as a cushioning plate to alleviate a shock at the time of engaging the clutch. In the power disconnecting clutch provided in the above described conventional torque convertor, the clutch is rapidly engaged, so that a shock is produced at the time of engagement. This shock at the time of engagement is transmitted to the speed change gear side through the output-side member, thereby to cause noise.
Furthermore, the above described conventional torque convertor is inferior in discharge characteristics because it is so constructed that lubricating oil stored in the space where the power disconnecting clutch is disposed is discharged outward through winding oil passages, resulting in energy loss due to the inertia of the hydraulic fluid and aggravating the above described problem of the drag torque.
Furthermore, examples of the conventional torque convertor include one provided with a lock-up clutch for transmitting power by directly connecting an input-side rotation member and a power disconnecting clutch to each other. In the conventional torque convertor, the power disconnecting clutch has been already disposed laterally of the torque convertor body. If the lock-up clutch is installed, therefore, the axial length of the entire torque convertor is increased.
Additionally, in the torque convertor, hydraulic operating fluid and lubricating oil are generally supplied by an oil pump fixed to a housing on the speed change gear side. The hydraulic operating fluid pumped up by the oil pump is supplied to respective portions by a control valve through oil passages. The oil pump is generally driven utilizing the rotation of the input-side rotation member in the torque convertor. Specifically, an oil pump gear fixed to a part of the torque convertor engages with a driving gear of the oil pump. If the torque convertor is rotated, the oil pump gear is rotated, whereby the oil pump is driven. In such a structure, engaging portions of the oil pump gear and the driving gear of the oil pump are lubricated by an oil circuit exclusively provided. However, this circuit makes the structure complicated.
Furthermore, the above described torque convertor comprising with the torque convertor body and the power disconnecting clutch makes it possible for the conventional manual power transmission device to convert into a semi-automatic power transmission device. That is, if a vehicle having the conventional manual clutch device is equipped with the above described torque convertor having the torque convertor body and the power disconnecting clutch in place of the manual clutch, thereby to make it possible to shift gear without depressing a clutch pedal. In this case, it is desirable to exchange the clutch device without altering the other portions of the vehicle equipped with the manual speed change gear.